Oxygen Diffusivity in Avocado Fruit Tissue

The oxygen mass diffusion coefficient in pre-climacteric ‘Hass’ avocado fruits tissue at 20 °C was evaluated. A respiration–diffusion model was developed by using a non-steady–state mass balance routine, in combination with the second law of Fick and the Michaelis–Menten enzymatic kinetic theory. Diffusivity was determined by simulation trials where a set of quantities for this parameter was proposed during the model solution, until a predicted O2 partial pressure below the skin agreed with experimental information; the resulting value was 2·2×10−9 m2 s−1. The effect of the diffusion on the respiration parameters is discussed. Oxygen internal concentration profiles were used to suggest a minimal permissible coating permeance for an adequate fruit modified atmosphere storage.